Low-temperature synthesis of BiNbO4 ceramics using reaction-sintering process

Low-temperature synthesis of BiNbO₄ ceramics using reaction-sintering process was investigated. Orthorhombic BiNbO₄ phase together with minor triclinic BiNbO₄ phase were found in the pellets. The phase transition temperature in BiNbO₄ with 0.5 wt% CuO addition was lowered from 960 °C via traditional route to 880 °C when the reaction-sintering process was used. After 920 °C sintering for 4 and 6 h, densities 6.8–6.85 g/cm³ (94% of the theoretical value) were obtained. The abnormal grain growth in BiNbO₄ via traditional route was not observed in this study.     

An On-Site Cooling Tower Treated by Stand-Alone Low-Concentration Dissolved Ozone

We report on an on-site 500 RT cooling tower ozone treatment process, in which chemicals other than ozone itself were completely eliminated. Ozone in an amount leading to less than 0.1 ppm of dissolved ozone was continuously introduced via side-stream injection into the circulating water returning from the chiller. The ozonated water was initially made to flow from the distributor to the filler in order to eliminate the growth of algae, and then to the chiller to reduce the corrosion and the fouling in the water. Positive ions such as Ca⁺² and Mg⁺² in the circulating water were precipitated by chelating them with carboxylic acids formed by the oxidation of organic compounds. We observed that using an ozone dosage of 0.1 ppm resulted in a colony-forming unit (CFU) less than 2 × 10³ /mL. With that well-controlled CFU, corrosion controlling and scale reducing were achieved as well.     

Electrochemical pitting behaviour of type 321 stainless steel in sulfide-containing chloride solutions

The pitting behaviour of type 321 stainless steel in sulfide-containing chloride aqueous environments was studied using cyclic potentiodynamic polarization. A well-established correlation between H₂S and Na₂S₂O₃ in the study of corrosion was applied, that is, H₂S was simulated by Na₂S₂O₃. The major factors affecting the pitting corrosion of type 321 stainless steel are the Cl^- concentration, solution pH and temperature. The results clearly indicate that both E_pit and E _pp decrease with increasing Cl^- concentration and temperature, while I _pass is more sensitive to temperature variation. E _pit decreased with decreasing pH in the range 2 < pH < 7.5. The surface morphology and chemistry of the corroded type 321 stainless steel resulting from anodic polarization in 0.01 M S₂O ₃ ^2- -containing Cl^- solution were analysed by XRD, SEM and EPMA. A higher concentration of sulfur was found in the pits, and the dark surface film was mainly composed of FeS and -Fe₂O₃. The results describe the pitting behaviour of type 321 stainless steel in sulfide-containing Cl^- aqueous environments.     

A numerical approach of interaction of methane thermocatalytic decomposition and microwave irradiation

Thermocatalytic decomposition (TCD) of methane in association with microwave heating is a route to produce hydrogen without the formation of CO and CO₂. To recognize the interaction characteristics of methane TCD and microwave irradiation in an activated carbon catalyst bed, the chemical reaction along with microwave-assisted heating is modeled and simulated numerically. The influences of microwave power, volumetric hourly space velocity (VHSV), and catalyst bed geometry on the performance of methane TCD are investigated. The predictions suggest that a higher microwave power can efficiently promote the performance. Increasing VHSV reduces CH₄ conversion because of the lower residence time of methane in the catalyst bed; nevertheless, more hydrogen is produced. A smaller diameter of catalyst bed facilitates the chemical reaction. The distributions of temperature, reaction rate, and electric and magnetic fields in the catalyst bed at various operating conditions can be clearly observed. Consequently, the developed method and predictions are able to aid in figuring out the reaction phenomena of experimental work and designing the reactor for achieving methane TCD.     

A method to extract mobility degradation and total seriesresistance of fully-depleted SOI MOSFETs

Free-carrier mobility degradation in the channel and drain/source series resistance are two important parameters limiting the performance of MOS devices. In this paper, we present a method to extract these parameters from the drain current versus gate voltage characteristics of fully-depleted (FD) SOI MOSFETs operating in the saturation region. This method is developed based on an integration function which reduces errors associated with the extraction procedure and on the DC characteristics of MOS devices having several different channel lengths. Simulation results and measured data of FD SOI MOSFETs are used to test and verify the method developed     

Bandwidth-expandable erbium-doped fiber amplets

A narrow-band optical amplifier (“amplet”) is proposed and demonstrated that can be constructed into an amplifier-based subsystem to perform nonlinear dispersion compensation and to flatten gain while the input level changes in a dense wavelength-division-multiplexed (DWDM) optical networking system. The amplet is designed to inherently provide two networking features: narrow-band accessibility and bandwidth scalability. For a 100-GHz-spaced DWDM application, each amplet can process four channels. The crosstalk between amplets is better than 58 dB. The capability to flatten gain and improve the transient response is experimentally demonstrated when an amplet array subsystem is formed     

Design of micro-retainer to counter-balance spinning seismic proof mass

An innovative magnetic module which is concurrently capable of performing as an actuator and a sensor is proposed and analyzed. The magnetic module is basically similar to a micro-scale Linear Variable Differential Transformer (LVDT) which is employed to actively adjust the height of a rotating seismic disc used in a gyroscope so that the pitch rate induced by Coriolis effect, due to exerted angular excitation, can be accurately measured. That is, the micro-magnetic module acts like an actuator for height regulation on the seismic proof mass by applying appropriate electric current to the primary winding of the LVDT unit. On the other hand, the secondary winding pair of the LVDT acts like a sensor which can detect the gap change, between the seismic rotating disc and the micro-magnetic LVDT module, and the rotation speed (i.e., frequency) by the induced current.     

Influence of channel aspect ratio on heat transfer in rotating rectangular ducts with skewed ribs at high rotation numbers

Centerline heat transfer measurements along two opposite ribbed walls in three rotating rectangular ducts roughened by 45° staggered ribs with channel aspect ratios (AR) of 1:1, 2:1 and 4:1 are performed at Reynolds (Re), rotation (Ro) and buoyancy (Bu) numbers in the ranges of 5000–30,000, 0–2, and 0.005–8.879, respectively. These channel geometries are in common use as the internal cooling passages of a gas turbine rotor blade and the tested Ro and Bu ranges are considerably extended from the previous experiences. This study focuses on the heat transfer characteristics in response to the change of AR under the parameter ranges examined. With zero-rotation (Ro = 0), the local Nusselt numbers (Nu₀) along the centerlines of two opposite ribbed walls increase as AR increases due to the increased rib-height to channel-height ratio. The Bu impact on heat transfer appears to be AR dependent, i.e. the increase of Bu elevates Nusselt number ratios Nu/Nu₀ in the square channel but impairs heat transfer in the rectangular channels of AR = 2 and 4. Acting by the Coriolis effect alone, all the leading edge Nu values in the present Ro range are lower than the zero-rotation references but started to recover as Ro increases from 0.1 in the channels of AR = 1, 2 and from 0.3 in the channel of AR = 4. The trailing edge Nu/Nu₀ ratios increase consistently from unity as Ro increases but their responses toward the increase of AR are less systematic than those found along the leading edge. The above findings, with the aids of extended Ro and Bu ranges achieved by this study, serve as the original contributions for this technical community. The Nu/Nu₀ ratios in the rotating channels of AR = 1, 2, and 4 fall in the ranges of 0.6–2.2, 0.5–2.7, and 0.5–2.1, respectively. A set of heat transfer correlations is derived to represent all the heat transfer data in the periodically developed flow regions of three rotating ducts.     

A First-Order Model for Depolarization of Propagating Signals by Narrowband Ricean Fading Channels

We show by simulation that when the fading signals observed on orthogonally polarized diversity branches follow Ricean statistics, the distribution of polarization states on the Poincar′e sphere is well-approximated by a Fisher distribution. Further, we show that the Fisher concentration parameter is: (1) completely determined by the corresponding Ricean Kfactors and the cross-correlation coefficient between the diversity branches, both of which can be estimated from simple measurements of received power vs. time, and (2) a good indicator of the level of cross-polar discrimination (XPD) on the channel. The insights gained are potentially useful to those engaged in the development and validation of schemes that use either polarization re-use or polarized MIMO.     

复合型高效捕沫器在甲醇分离器中的应用

简述了甲醇装置甲醇分离器的基本结构和技改前存在的问题,介绍了复合型高效捕沫器的基本原理以及应用于甲醇分离器的实际效果,分析了技改中有待解决的问题和原因。技改效果表明,采用复合型高效捕沫器后,甲醇分离器的分离效率由28.9%提高至94.4%;技改投资为30万元/套,投资回收期为2个月。